Interview Q&A

Short answer: Express.js is a fast, minimal, and flexible Node.js web framework. It simplifies building web applications and APIs by handling routing, middleware, requests, responses, and more. ✅ It’s like jQuery for the backend — removes the boilerplate.

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Applications and APIs by handling routing, middleware, requests, responses, and more. ✅ It’s like jQuery for the backend — removes the boilerplate.

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: An operation is idempotent if repeating it has the same effect as doing it once (e.g., PUT). Important for safe retries.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.get('/users/:id', (req, res) => { const id = req.params.id; res.send(`User ID: ${id}`); }); Request to /users/42 returns: User ID: 42 pp.get('/users/:id', (req, res) => { const id = req.params.id; res.send(`User ID: ${id}`); }); Request to /users/42 returns: User ID: 42 pp.get('/users/:id', (req, res) => { const id = req.params.id; res.send(`User ID:… ${id}`); }); Request to /users/42 returns: User ID: 42…

Explain a bit more

pp.get('/users/:id', (req, res) => { const id = req.params.id; res.send(`User ID: ${id}`); }); Request to /users/42 returns: User ID: 42

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Stateless: Each request is independent; no session stored on server. Stateful: Server keeps session info (like login status). Stateless apps scale easier. Testing & Debugging

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Middleware is a function that runs between the request and response cycle. It can: Modify request/response Execute logic Call the next middleware 📌

Example code

app.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); // Move to next middleware or route });

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); // Move to next middleware or route }); pp.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); // Move to next middleware or route }); pp.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); // Move to next middleware or route });… pp.use((req, res, next) => { console.log(`${req.method}…

Explain a bit more

${req.url}`); next(); // Move to next middleware or route });

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Method Purpose app.use () Middleware for all requests app.get () Handle only GET requests 📌

Example code

app.use(authMiddleware); // Runs on all routes app.get('/data', handler); // Runs only for GET /data

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Write tests before code, then develop just enough to pass tests. Use frameworks like Mocha or Jest.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.use () Middleware for all requests pp.get () Handle only GET requests 📌 pp.use(authMiddleware); // Runs on all routes pp.get('/data', handler); // Runs only for GET /data pp.use () Middleware for all requests pp.get () Handle only GET requests 📌

Example code

pp.use(authMiddleware); // Runs on all routes pp.get('/data',… handler); // Runs only for… pp.use () Middleware for all requests pp.get () Handle only GET requests 📌 Example: pp.use(authMiddleware); // Runs on all routes pp.get('/data', handler); // Runs only for GET /data pp.use () Middleware for all requests pp.get () Handle only GET requests 📌 Example: pp.use(authMiddleware); // Runs on all routes pp.get('/data',… handler); // Runs only for GET /data

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pp.use((req, res) => { res.status(404).json({ message: 'Route not found' }); }); pp.use((req, res) => { res.status(404).json({ message: 'Route not found' }); }); pp.use((req, res) => { res.status(404).json({ message: 'Route not found' }); }); pp.use((req, res) => { res.status(404).json({ message: 'Route not found' }); });

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Node Version Manager lets you install and switch between Node.js versions easily.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: npm: Default Node package manager. yarn: Faster installs, better caching. pnpm: Efficient disk usage by linking packages.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Babel: Transpiles modern JS to compatible versions. TypeScript: Adds static typing and compiles to JS.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Rate limiting prevents abuse by limiting the number of requests a user can make in a given time. 📌 Use express-rate-limit: npm install express-rate-limit const rateLimit = require('express-rate-limit'); const limiter = rateLimit({ windowMs: 15 * 60 * 1000, max: 100 // limit per IP }); app.use(limiter);

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.